Fourier finite-difference migration of internal multiples

The conventional seismic migration method employs primaries to perform migration imaging only and the multiples, regarded as a kind of noise, need to be removed before imaging. However, the migration of multiples has a higher illuminance than the imaging for primaries, which can improve the accuracy of seismic imaging. The modified Fourier finite-difference migration uses internal multiples as input data to image the internal multiple. The Fourier finite-difference migration method of internal multiples presented in this paper applies wavefield extrapolation and full-wavefield method to compute the upward and downward wavefields and then uses cross-correlation condition to image the internal multiples of different orders separately. The forward and reverse wavefields are cross-correlated at t = 0. Numerical examples verify the correctness and practicability of the proposed method and show that internal multiples imaging can highlight the events of salt, restore the structural information under the salt, make up for the shortcomings of the conventional migration methods, significantly improve seismic imaging resolution, and effectively provides additional illumination for the underground.